The present invention relates to a method for manufacturing an elastic composite body with a plurality of metal wires embedded therein or bonded thereon in alignment so as to impart anisotropic electroconductivity to the body, which is useful as a connector for electrically connecting two electronic circuit boards, electromagnetic shielding gasket, thermally conductive gasket and the like.
There have been widely used in the art in the above mentioned applications a variety of elongated rod-like composite bodies composed of an elastomer or a plastic body and a plurality of metal wires each extending in the transverse direction of the elongated body in substantially parallel alignment with each other as embedded therein or bonded on the surface so as that the elongated body is imparted with electroconductivity in the transverse direction but insulating in the longitudinal direction.
Basically and most simply, each of the metal wires in or on the elongated body can be in a straightened form in order that the composite body is most conveniently manufactured. Recently, there are proposed composite bodies of the kind in which each of the metal wires embedded in or bonded on the surface of the elongated body of rubber or plastic is curved, bent or corrugated in a wavy form (see, for example, U.S. Pat. Nos. 3,708,871 and 3,795,037 and Japanese Patent Disclosure No. 48-91580) which is the equivalent to U.S. Pat. No. 3,852,878. The composite bodies with such curved, bent or corrugated metal wires are advantageous in the increased elastic resilience when the composite body is under compression in the direction parallel to the longitudinal direction of the aligned metal wires by virtue of the resilience caused by the elastic deformation of the metal wires supplementing the elasticity of the rubber or plastic matrix.
The composite bodies with curved, bent or corrugated metal wires are manufactured in a variety of procedures as is known from the above mentioned prior art references. In any way, however, the metal wires or ribbons are in advance deformed and shaped to have a desired curved, bent or corrugated form and the thus deformed metal wires are then integrated with the rubber or plastic matrix material to be embedded therein or bonded thereon. Such a manufacturing procedure is, however, somewhat defective due to the difficulty in obtaining satisfactory uniformity or exactness of the alignment of the metal wires. For example, curved or bent wires can not always be in exact parallelism with each other and corrugated wires have no satisfactory conformability with respect to the phase of the corrugated waves in or on the elongated body.
The above mentioned irregularity in the alignment of the metal wires naturally leads to the localized irregularity of the resilience of the composite body as a whole so that an unduly larger compressive force is required for holding the composite body with compression in a narrow space between two holding planes than otherwise. In addition, some of the metal wires receive an excessively large compressive force over others so that they are increasingly subject to elastic fatigue with dereased reproducibility in the contacting condition which is undesirable from the standpoint of obtaining constant electroconductivity performance with constant compressive load in the repeated use of the composite body.
The manufacturing procedures disclosed in the latter two of the above mentioned prior art references are relatively free from the above described problem of the irregularity in the alignement of the metal wires. These procedures are, however, very complicated and troublesome with rather low yield of the products so that defective from the standpoint of practical production.